https://gcc.gnu.org/bugzilla/show_bug.cgi?id=127098
--- Comment #3 from Georg-Johann Lay <gjl at gcc dot gnu.org> ---
It's actually already there in .expand:
;; Generating RTL for gimple basic block 2
;; fun (0, u.0_1);
(insn 5 4 6 (set (reg/f:HI 32 __SP_L__)
(plus:HI (reg/f:HI 32 __SP_L__)
(const_int -16 [0xfffffffffffffff0]))) "pr127098.c":19:3 -1
(expr_list:REG_ARGS_SIZE (const_int 16 [0x10])
(nil)))
(insn 6 5 7 (set (reg:QI 45)
(mem/c:QI (symbol_ref:HI ("u") [flags 0x2] <var_decl # u>) [0 u+0 S1
A128])) "pr127098.c":19:3 -1
(nil))
(insn 7 6 8 (set (mem:QI (plus:HI (reg/f:HI 32 __SP_L__)
(const_int 16 [0x10])) [0 S1 A128])
(reg:QI 45)) "pr127098.c":19:3 -1
(nil))
